A mouse is a box-shaped input device including a ball arranged therein to expose from the bottom side, and is used primarily with personal computers. The mouse is manipulated to run on the surface of a desk or the like when used. A mouse pad is also often employed to make the mouse run in a more stable manner and to achieve accurate input operation. As shown in FIG. 5, a conventional mouse pad B is formed of a plate being substantially uniform in thickness, and is made of vinyl chloride or the like.